Machine Production of Steamed Buns (Meat Buns, Vegetable Buns, Red Bean Buns)

Steamed buns (包子) are one of the most classic applications of encrusting machines. According to the company history on Japan's RHEON website, founder Torahiko Hayashi developed the automatic encrusting machine in 1961 (called 包あん機 in Japanese, which originally meant wrapping up sweet bean paste). The steamed bun machines on the market today, whether made in Japan, Taiwan, or China, mostly extend from this principle.

What Machine Is Used for Steamed Buns?

The basic operation of a steamed bun machine (also called an encrusting and forming machine in the industry):

1. Dough and filling are loaded into two separate hoppers.
2. The dough is pushed into a tube while filling is fed simultaneously through the center of the tube, forming a continuous rope with "dough outside, filling inside."
3. At the outlet, a cutting device (a shutter or blade) cuts the rope section by section and seals it, forming balls.
4. The balls drop onto the conveyor and are sent on for shaping and panning.

The ratio of dough to filling and the weight of each piece can be changed by adjusting the feed speed on each side. RHEON's U.S. website describes the CORNUCOPIA KN551 as making up to 100 pieces per minute at 10–300 g per piece, with products including steam buns and BBQ pork buns.

Dong-Yih Machinery's website describes the DY-201 Automatic Steamed Bun and Mantou Machine as using a "traditional technique" that does not break down the dough structure. Its output is 2,000–12,000 pieces/hour with 2.0 kW of power, and it can produce meat buns, vegetable buns, red bean buns, taro buns, scallion rolls, two-color mantou, xiaolongbao, mini mantou, longevity peach buns, French bread, and filled bread, as well as silver thread rolls, gua bao, and silver thread flower rolls.

How Are Pleats Made?

The pleats on top of a steamed bun are the feature many customers care about most. Machines commonly make pleats in two ways:

• Pleats formed directly during forming: The sealing mechanism twists as it closes, leaving radial pleat marks.
• Pleating after encrusting: After the ball is formed, it passes through a dedicated pleating unit that presses pleats into the top. RHEON's Japanese website lists the "Chinese-style steamed bun pleating machine" (中華まんヒダ付け機) as a peripheral for encrusting machines, used to add pleats to the tops of formed products.

The number of pleats, their depth, and whether the seal has a small peak all depend on the mechanism's design. Sweet buns such as red bean and taro buns are often made with smooth, domed tops and do not necessarily need pleats.

What to Watch for When Running Fermented Dough on a Machine

Steamed bun dough is a fermented dough that stays "alive," so pay special attention when running it on a machine:

• Temperature: The warmer the dough in the hopper, the faster it ferments, and weight and volume will drift between earlier and later batches. In summer, watch the water temperature for mixing and the working environment.
• Relaxing and degassing: Dough with too many air bubbles extrudes unsteadily, and the wrapper thickness becomes uneven. Many lines sheet or degas the dough first.
• Dusting flour: Too little and the buns stick to the conveyor; too much and flour spots show on the surface after steaming.
• Filling: Meat filling that is too runny will leak, and vegetable filling must be dewatered first; red bean paste should be close in firmness to the dough so the wrapper comes out even.

This is also why RHEON's Japanese website treats its encrusting machine "for fermented dough" (KASEIJIN (火星人) CN601) as a separate model: fermented dough has different flow characteristics from ordinary wagashi dough.

How Should a Steamed Bun Line Be Set Up?

A common steamed bun line:

1. Dough mixing (mixer) → sheeting or conditioning the dough
2. Filling preparation (meat grinder, vegetable dewaterer, mixer)
3. Forming on the bun machine (including pleating)
4. Panning → final proofing (proofer)
5. Steaming (steam cabinet or continuous steamer)
6. Cooling → blast freezing → packaging

The capacity of final proofing and steaming is often the bottleneck: if the bun machine makes thousands of buns an hour but the proofer and steam cabinet cannot hold them, it does no good. In addition, raw-frozen (frozen right after forming, with customers proofing and steaming them themselves) and cooked-frozen (steamed, then frozen) processes differ, so how you sell determines what the line looks like.

For mantou and flower rolls, see Machine Production of Mantou, Flower Rolls, Silver Thread Rolls, and Gua Bao; for xiaolongbao, see Machine Production of Xiaolongbao and Soup Dumplings.

FAQ

Q: How many buns can a steamed bun machine make per hour?
A: It depends on the model. Dong-Yih's website lists the DY-201 at 2,000–12,000 pieces/hour.

Q: Do machine-made buns have pleats?
A: They can. Some models form pleats directly during sealing, while others connect a separate pleating unit. The pleat style depends on the mechanism.

Q: Can meat buns, vegetable buns, and red bean buns be made on the same machine?
A: Most encrusting machines can make different flavors simply by changing the filling; Dong-Yih's website lists meat buns, vegetable buns, red bean buns, and taro buns for the DY-201. Clean the filling system when changing flavors.

Q: What flour should be used for a bun machine?
A: There is no single answer; all-purpose flour and bun-specific flour are both common. The key is keeping dough firmness and fermentation consistent. We recommend bringing your own recipe for a test run.

Q: Should buns be steamed or frozen first?
A: Both approaches exist. Raw-frozen means freezing right after forming; cooked-frozen means steaming, cooling, and then freezing. The line equipment differs.